General Description
Table 1: EIA and MIL Temperature Stable and General
Application Codes
EIA CODE
Percent Capacity Change Over Temperature Range
RS198
X7
X6
X5
Y5
Z5
Code
D
E
F
P
R
S
T
U
V
Temperature Range
-55°C to +125°C
-55°C to +105°C
-55°C to +85°C
-30°C to +85°C
+10°C to +85°C
Percent Capacity Change
±3.3%
±4.7%
±7.5%
±10%
±15%
±22%
+22%, -33%
+22%, - 56%
+22%, -82%
Effects of Voltage –
Variations in voltage have little effect
on Class 1 dielectric but does affect the capacitance and
dissipation factor of Class 2 dielectrics. The application of
DC voltage reduces both the capacitance and dissipation
factor while the application of an AC voltage within a
reasonable range tends to increase both capacitance and
dissipation factor readings. If a high enough AC voltage is
applied, eventually it will reduce capacitance just as a DC
voltage will. Figure 2 shows the effects of AC voltage.
Cap. Change vs. A.C. Volts
X7R
Capacitance Change Percent
50
40
30
20
10
0
12.5
25
Volts AC at 1.0 KHz
37.5
50
EXAMPLE – A capacitor is desired with the capacitance value at 25°C
to increase no more than 7.5% or decrease no more than 7.5% from
-30°C to +85°C. EIA Code will be Y5F.
Figure 2
MIL CODE
Symbol
A
B
C
Symbol
R
S
W
X
Y
Z
Temperature Range
-55°C to +85°C
-55°C to +125°C
-55°C to +150°C
Cap. Change
Zero Volts
+15%, -15%
+22%, -22%
+22%, -56%
+15%, -15%
+30%, -70%
+20%, -20%
Cap. Change
Rated Volts
Capacitor specifications specify the AC voltage at which to
measure (normally 0.5 or 1 VAC) and application of the
wrong voltage can cause spurious readings. Figure 3 gives
the voltage coefficient of dissipation factor for various AC
voltages at 1 kilohertz. Applications of different frequencies
will affect the percentage changes versus voltages.
D.F. vs. A.C. Measurement Volts
X7R
10.0
Dissipation Factor Percent
Curve 1 - 100 VDC Rated Capacitor
8.0 Curve 2 - 50 VDC Rated Capacitor
Curve 3 - 25 VDC Rated Capacitor
6.0
4.0
2.0
0
.5
1.0
1.5
2.0
2.5
AC Measurement Volts at 1.0 KHz
Curve 1
Curve 3
Curve 2
+15%, -40%
+22%, -56%
+22%, -66%
+15%, -25%
+30%, -80%
+20%, -30%
Temperature characteristic is specified by combining range and
change symbols, for example BR or AW. Specification slash sheets
indicate the characteristic applicable to a given style of capacitor.
In specifying capacitance change with temperature for Class
2 materials, EIA expresses the capacitance change over an
operating temperature range by a 3 symbol code. The first
symbol represents the cold temperature end of the temper-
ature range, the second represents the upper limit of the
operating temperature range and the third symbol repre-
sents the capacitance change allowed over the
operating temperature range. Table 1 provides a detailed
explanation of the EIA system.
Figure 3
Typical effect of the application of DC voltage is shown in
Figure 4. The voltage coefficient is more pronounced for
higher K dielectrics. These figures are shown for room tem-
perature conditions. The combination characteristic known
as voltage temperature limits which shows the effects of
rated voltage over the operating temperature range is
shown in Figure 5 for the military BX characteristic.
66
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